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Ablation
Ablation is the removal of material from the surface of an object by vaporization, chipping, or other erosive processes. Examples of ablative materials biological tissues in medicine. This process results in lesions In medicine, ablation is the same as removal of a part of biological tissue, usually by surgery. Surface ablation is also employed in otolaryngology for several kinds of surgery, such as for snoring. Ablation therapy using radio frequency waves on the heart is used to cure a variety of cardiac arrhythmia such as supraventricular tachycardia, Wolff–Parkinson–White syndrome (WPW), ventricular tachycardia, and more recently as management of atrial fibrillation. The term is often used in the context of laser ablation, a process in which a laser dissolves a material's molecular bonds. For a laser to ablate tissues, the power density or fluence must be high, otherwise thermocoagulation occurs, which is simply thermal vaporization of the tissues. Rotoablation is a type of arterial cleansing that consists of inserting a tiny, diamond-tipped, drill-like device into the affected artery to remove fatty deposits or plaque. The procedure is used in the treatment of coronary heart disease to restore blood flow. Radiofrequency ablation (RFA) is a method of removing aberrant tissue from within the body via minimally invasive procedures. I.e., RFA in an electrophysiology study to remove cells that are issuing abnormal electrical activity leading to arrhythmia. Surgery Ablation of brain tissue is used for treating certain neurological disorders, particularly Parkinson's disease, and sometimes for psychiatric disorders as well. Laser ablation Laser ablation is greatly affected by the nature of the material and its ability to absorb energy, therefore the wavelength of the ablation laser should have a minimum absorption depth. While these lasers can average a low power, they can offer peak intensity and fluence given by: : \text{Intensity } (\mathrm{W}/\mathrm{cm}^2) = \frac{\text{average power } (\mathrm{W})}{\text{focal spot area } (\mathrm{cm}^2)} : \text{Peak intensity } (\mathrm{W}/\mathrm{cm}^2) = \frac{\text{peak power } (\mathrm{W})}{\text{focal spot area } (\mathrm{cm}^2)} : \text{Fluence } (\mathrm{J}/\mathrm{cm}^2) = \frac{\text{laser pulse energy } (\mathrm{J})}{\text{focal spot area } (\mathrm{cm}^2)} while the peak power is : \text{Peak power } (\mathrm{W}) = \frac{\text{pulse energy } (\mathrm{J})}{\text{pulse duration } (\mathrm{s})} Surface ablation of the cornea for several types of eye refractive surgery is now common, using an excimer laser system (LASIK and LASEK). Since the cornea does not grow back, laser is used to remodel the cornea refractive properties to correct refraction errors, such as astigmatism, myopia, and hyperopia. Laser ablation is also used to remove part of the uterine wall in women with menstruation and adenomyosis problems in a process called endometrial ablation. Recently, researchers have demonstrates a successful technique for ablating subsurface tumors with minimal thermal damage to surrounding healthy tissue using a focused laser beam from an ultra-short pulse diode laser source. Amir Yousef Sajjadi, Kunal Mitra, Michael Grace, Ablation of subsurface tumors using an ultra-short pulse laser, Optics and Lasers in Engineering, Volume 49, Issue 3, March 2011, Pages 451-456, ISSN 0143-8166 Genetics Genetic ablation is another term for gene silencing, in which gene expression is abolished through the alteration or deletion of genetic sequence information. In cell ablation, individual cells in a population or culture are destroyed or removed. Both can be used as experimental tools, as in loss-of-function experiments.Cell Ablation definition at Change Bioscience. Recently, some researchers reported successful results with genetic ablation. In particular, genetic ablation is potentially a much more efficient method of removing unwanted cells, such as tumor cells, because large numbers of animals lacking specific cells could be generated. Genetically ablated lines can be maintained for a prolonged period of time and shared within the research community. Researchers at Columbia University report of reconstituted caspases combined from C. elegans and humans, which maintain a high degree of target specificity. The genetic ablation techniques described could prove useful in battling cancer. Biology Biological ablation is the removal of a biological structure or functionality. See also * Axotomy * Castration * Chemical lesions * Decerebration * Decortication * Lesion methods * Neural lesions * Neurectomy * Neurosurgery * Psychosurgery * Radio frequency nerve lesioning References Category:Lesions